[newlib-cygwin] yield: Don't lower thread priority, it leads to starvation

Corinna Vinschen corinna@sourceware.org
Wed Mar 8 16:44:00 GMT 2017


commit 51a993c266581ba41f1622abd274d9848a37cf1d
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Wed Mar 8 17:44:15 2017 +0100

    yield: Don't lower thread priority, it leads to starvation
    ...and it's not required anymore to have the same effect as the original
    code post-XP.
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

 winsup/cygwin/miscfuncs.cc | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/winsup/cygwin/miscfuncs.cc b/winsup/cygwin/miscfuncs.cc
index 2117eb9..e2ab7a0 100644
--- a/winsup/cygwin/miscfuncs.cc
+++ b/winsup/cygwin/miscfuncs.cc
@@ -85,17 +85,18 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
 yield ()
-  int prio = GetThreadPriority (GetCurrentThread ());
-  SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE);
-  /* MSDN implies that SleepEx will force scheduling of other threads.
+  /* MSDN implies that Sleep will force scheduling of other threads.
      Unlike SwitchToThread() the documentation does not mention other
      cpus so, presumably (hah!), this + using a lower priority will
      stall this thread temporarily and cause another to run.
      (stackoverflow and others seem to confirm that setting this thread
      to a lower priority and calling Sleep with a 0 paramenter will
-     have this desired effect)  */
+     have this desired effect)
+     CV 2017-03-08: Drop lowering the priority.  It leads to potential
+		    starvation and it should not be necessary anymore
+		    since Server 2003.  See the MSDN Sleep man page. */
   Sleep (0L);
-  SetThreadPriority (GetCurrentThread (), prio);
 /* Get a default value for the nice factor.  When changing these values,

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